Most networks in the telecommunications networks of today include Passive Optical Networks (“PONs”). In PONs, generally most to all components which require power (“active components”), e.g., repeaters, relays, memory chips, processors, between the Central Office exchange and termination points at the customer premises are eliminated, and passive optical components are put into the network to guide traffic based on splitting the power of optical wavelengths to endpoints along the way. The passive splitters or couplers are merely devices working to pass or restrict light, and as such, have no power or processing requirements thereby lowering overall maintenance costs for the service provider.
FIG. 1 shows a typical PON 100 for an optical access architecture. As shown in FIG. 1, PON 100 includes an optical line terminator (“OLT”) 101 located at a Central Office (“CO”) and a set of optical network units (“ONU”) 103, or optical network terminals, located at the customer premise. Each of the ONU 103 is connected to the OLT 101 through feeder fiber 102, e.g., an outside fiber plant, optical power splitter 104, and individual distribution fibers 105. Feeder fiber 102 may transmit optical signals at 125 Megabits per second (“Mbps”), 155 Mbps, 622 Mbps, 1.25 Gigabits per second (“Gbps”), 2.5 Gbps, 10 Gbps, or 40 Gbps, in accordance with standards used for various access platforms. Various access platforms, including various transmission formats, and communication and control protocols, e.g., Ethernet based PON (“EPON”), Broadband PON (“BPON”), Gigabit PON (“GPON”), and ATM based PON (“APON”), has been developed to deliver information, e.g., data, voice, and video, from the Central Office to each of the customer premises.
Access platforms, e.g., EPON, BPON, or GPON, use light having a wavelength of 1.49 microns (“um”) to transmit information in downstream 106 direction and light having the wavelength of 1.3 um to transmit information in upstream 107 direction between the Central Office and the customer premises. OLT 101 contains a high power distributed feedback (“DFB”) laser to produce the light at 1.49 um in downstream 106 direction, which is shared by a plurality, e.g., 16, 32, or more of ONUs 103. For example, for EPON access platform, the bandwidth of optical signals having the wavelength of 1.49 um and data transmission rate of 1.25 Gbps is shared between a plurality of ONU 103 using optical power splitter 104. Such configuration of a PON is inefficient because the power supplied to each of the ONUs 103 is reduced at least by the factor of 1/N, wherein N is the amount of ONUs 103 coupled to the power splitter.
ONU 103 typically uses lasers to produce light at 1.3 um within a large optical bandwidth of over 100 nm in upstream 107 direction. The wavelength of the light produced by such lasers may vary with the device distributing the light of the laser, time, temperature, or any other condition.
OLT 101 may service the plurality of ONU 103 through the use of optical power splitter 104 and access platform PON protocols to control the sending and transmission of signal across the shared access facility. Data may be transmitted downstream 106 from OLT 101 to each of ONU 103, and each ONU 103 processes the data destined to it by matching the address at the access protocol transmission unit header. Upstream 107 data from each of the ONU 103 to OLT 101 is transmitted according to access control mechanisms and protocols in the OLT 101, which include a time division multiplexing scheme, in which dedicated transmission time slots are granted to each individual ONU 103, to avoid data collision. As such, transport of information between the Central Office and customer premises depends on the type of the access platform used by the Central Office and customer premises. Further, each OLT 101 at the Central Office requires its own feeder fiber 102 to provide data transmission to and from the plurality of ONUs 103. In addition, a timing algorithm may be used in existing access platforms, which limits the distance between the OLT 101 and ONU 103 to 20 km.
Sharing the same bandwidth between a plurality of ONU 103 in an existing access platforms is not only inefficient, it also can give rise to security issues, because data transmitted from OLT 101 downstream may go to every user. This can produce an additional level of complexity to the data transmission, sometimes requiring scrambling the data code, data encryption, and the like.